| Traditional Deployment Methods | 47
2. Configure and save the following settings:
Parameter Description Configuration Method
Static NAT/Type Select Manual/Manual
Settings, and then configure the
NAT address manually.
Web user interface
Endpoint
CTP20
NAT Public IP Address/Public
IP Address
Configure the NAT address for
the system manually.
Web user interface
Endpoint
CTP20
Route Traversal
Configure the route traversal
type.
• Auto—NAT works only when
making a call to a public
address. NAT does not work
when making a call to a
private address.
• Compulsion—NAT works
whatever you are making a
call to a public address or
private address.
Default: Auto.
Web user interface
3. Apply the route traversal settings to the SIP protocol.
Related tasks
Enabling Static NAT Feature for SIP Protocol(SIP Account and SIP IP Call)
STUN
If you want to use the VCS in the intranet to place calls to the VCS in the extranet, you can use STUN server,
as well as configure ALG on the router or enable static NAT on the system.
STUN is a client/server protocol, which allows the system behind a NAT to discover the NAT presence
firstly, and the mapped public IP address, and then the port number that the NAT has allocated for the UDP
flows to remote parties. Those information is used to establish UDP communication between two system
behind the NATs.
STUN is a client/server protocol. The system works as a STUN client, sending exploratory STUN messages to
the STUN server. After that, the STUN server uses those messages to determine the public IP address and
the port (which is used to connect the public network to the intranet), and then informs the client. For more
information, refer to RFC3489.
Capturing packets after you enable the STUN feature, you can find that the VCS sends Binding Request to
the STUN server, and then the mapped IP address and the port are placed in the Binding Response: Binding
Success Response MAPPED-ADDRESS: 59.61.92.59:19232
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